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Expression and distribution of grp-78/bip in mineralizing tissues and mesenchymal cells.

ABSTRACT: Glucose-regulated protein 78 (GRP-78) is one of the many endoplasmic reticulum chaperone proteins that have been shown to possess multifunctional roles. We have previously demonstrated that GRP-78 functions as a receptor for dentin matrix protein 1 (DMP1) and is required for DMP1-mediated calcium release; that it is a secreted protein and can bind to type I collagen and DMP1 extracellularly and aid in the nucleation of calcium phosphate. We provide evidence in this study that tyrosine phosphorylation is required for DMP1/GRP-78-mediated calcium release in mesenchymal cells. We further demonstrate that GRP-78 is localized in the nucleus of mesenchymal cells and that the cell surface GRP-78 is not associated with the G-protein G?q in mesenchymal cells. Results from this study show that during development of mineralized tissues, increased expression of GRP-78 can be observed in condensing cartilage and mesenchymal cells of the alveolar bone, endochondral bone and dental pulp. Additionally, we show that GRP-78 is present in the mineralizing matrices of teeth, bone and in the extracellular matrix of differentiating human marrow stromal cells and dental pulp stem cells. Collectively, our observations provide a new perspective on GRP-78 with respect to mineralized matrix formation.

SUBMITTER: Ravindran S

PROVIDER: S-EPMC3646624 | biostudies-literature | 2012 Jul

REPOSITORIES: biostudies-literature

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Expression and distribution of grp-78/bip in mineralizing tissues and mesenchymal cells.

Ravindran Sriram S Gao Qi Q Ramachandran Amsaveni A Sundivakkam Premanand P Tiruppathi Chinnaswamy C George Anne A

Histochemistry and cell biology 20120417 1

Glucose-regulated protein 78 (GRP-78) is one of the many endoplasmic reticulum chaperone proteins that have been shown to possess multifunctional roles. We have previously demonstrated that GRP-78 functions as a receptor for dentin matrix protein 1 (DMP1) and is required for DMP1-mediated calcium release; that it is a secreted protein and can bind to type I collagen and DMP1 extracellularly and aid in the nucleation of calcium phosphate. We provide evidence in this study that tyrosine phosphoryl ...[more]

PMID: 22527697

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Project description:Bone biomineralization is a complex process in which type I collagen and associated non-collagenous proteins (NCPs), including glycoproteins and proteoglycans, interact closely with inorganic calcium and phosphate ions to control the precipitation of nanosized, non-stoichiometric hydroxyapatite (HAP, idealized stoichiometry Ca10(PO4)6(OH)2) within the organic matrix of a tissue. The ability of certain vertebrate tissues to mineralize is critically related to several aspects of their function. The goal of this study was to identify specific NCPs in mineralizing and non-mineralizing tissues of two animal models, rat and turkey, and to determine whether some NCPs are unique to each type of tissue. The tissues investigated were rat femur (mineralizing) and tail tendon (non-mineralizing) and turkey leg tendon (having both mineralizing and non-mineralizing regions in the same individual specimen). An experimental approach ex vivo was designed for this investigation by combining sequential protein extraction with comprehensive protein mapping using proteomics and Western blotting. The extraction method enabled separation of various NCPs based on their association with either the extracellular organic collagenous matrix phases or the inorganic mineral phases of the tissues. The proteomics work generated a complete picture of NCPs in different tissues and animal species. Subsequently, Western blotting provided validation for some of the proteomics findings. The survey then yielded generalized results relevant to various protein families, rather than only individual NCPs. This study focused primarily on the NCPs belonging to the small leucine-rich proteoglycan (SLRP) family and the small integrin-binding ligand N-linked glycoproteins (SIBLINGs). SLRPs were found to be associated only with the collagenous matrix, a result suggesting that they are mainly involved in structural matrix organization and not in mineralization. SIBLINGs as well as matrix Gla (γ-carboxyglutamate) protein were strictly localized within the inorganic mineral phase of mineralizing tissues, a finding suggesting that their roles are limited to mineralization. The results from this study indicated that osteocalcin was closely involved in mineralization but did not preclude possible additional roles as a hormone. This report provides for the first time a spatial survey and comparison of NCPs from mineralizing and non-mineralizing tissues ex vivo and defines the proteome of turkey leg tendons as a model for vertebrate mineralization.

Dataset Information

Expression and distribution of grp-78/bip in mineralizing tissues and mesenchymal cells.

Publications

Expression and distribution of grp-78/bip in mineralizing tissues and mesenchymal cells.

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